Method for selectively isolating hydrogen or helium using a natrolite-based zeolite, and novel natrolite-based zeolite

ABSTRACT

The present invention relates to selectively isolating gases using a natrolite-based zeolite, and more particularly, to a novel natrolite-based zeolite and to selectively isolating hydrogen and/or helium gas using a natrolite-based zeolite. The present invention is characterized in that gas containing hydrogen is brought into contact with a natrolite-based zeolite to selectively isolate the hydrogen. The present invention provides a sorbent which can selectively isolate hydrogen and/or helium, and provides a method for isolating the hydrogen and/or helium at room temperature or at a high temperature.

PRIORITY CLAIM

This application is a National Phase of PCT/KR2009/005350 filed Sep. 21,2009, which claims priority to Korean Patent Application No.10-2009-0009716 filed Feb. 6, 2009 and Korean Patent Application No.10-2009-0085610 filed Sep. 10, 2009.

TECHNICAL FIELD

The present invention relates to a novel natrolite-based zeolite and theselective separation of gases using the same, and more particularly to aprocess of selectively separating hydrogen or helium using anatrolite-based zeolite.

BACKGROUND ART

Molecular sieves, including zeolites, have very small pores, the size ofwhich is uniform within a variation of 0.1 Å and the shape of whichvaries depending on the framework structure of the molecular sieves, andthus these molecular sieves show unique shape-selective properties whichare not observed in amorphous oxides. Accordingly, these nanoporousmaterials have been used as ion exchangers, separating agents, catalystsor catalyst supports, in the fine chemical industry, the petrochemicalindustry, and the like [Kirk Othmer Encyclo. Chem. Technol., 1996, Vol.16, pp. 888]. The successful use of such nanoporous materials can bebecause new zeolites whose framework structures or compositions differfrom those of existing materials have been continuously developed forseveral years, thus making it possible to significantly improve manycommercially important chemical processes. Gallosilicate zeolitescomprising gallium and silicon as framework elements havephysicochemical and catalytic properties different from those ofaluminosilicate zeolite [Oil Gas J., 1985, Vol. 83, pp. 1288], and thusstudies on the synthesis thereof have been actively conducted, and morethan 20 types of gallosilicate zeolites having different frameworkstructures have been reported to date [Chem. Rev. 2000, Vol. 100, pp.2303].

Accordingly, the present inventor has conducted many studies tosynthesize a molecular sieve having a framework structure andcomposition different from those of known zeolites and molecular sieves.As a result, the present inventor has discovered one type ofgallosilicate zeolite having a novel composition and has found that thistype of zeolite has a significant effect on gas adsorption.

High-purity hydrogen can be used in almost all fields, includingindustrial basic materials and current energy systems such as generalfuels, semiconductors and fuel cells, and thus has received attention asa next-generation energy source that can substitute for existing energysystems based on electricity and gases. In order to achieve a hydrogenenergy system different from existing energy systems, a technology forproducing large amounts of hydrogen should be provided, because thehydrogen energy system should be used in commercial and domesticapplications in addition to existing industrial applications. Inlong-term economic terms, the production cost of hydrogen should belower than the production cost of fossil fuels. Known methods forproducing large amounts of hydrogen include: (1) a method of producinghydrogen by electrolysis of water, and (2) a method of producinghydrogen by steam reforming. The electrolysis method (1) will not becost-effective if high power is used, because the production costs ofthe products (hydrogen and oxygen) greatly depends on the amount ofpower. For this reason, studies on systems, which produce inexpensivepower by renewable energy such as wind force or solar energy and producehydrogen by electrolysis using the produced power, have recently beenconducted, but such systems are difficult to use in practice due to manytechnical problems. Thus, under current circumstances, the steamreforming method (2) is the most suitable method for producing largeamounts of hydrogen. The steam reforming method is a method of obtaininghydrogen gas from natural gas and heavy naphtha which is a byproduct ofan oil refining process. In the steam reforming process, suchhydrocarbons are converted into synthesis gases, such as CO, CO₂ and H₂,by allowing them to react with steam at a high temperature of about 800°C. using nickel oxide as a catalyst. Herein, the obtained synthesisgases are treated by a gas separation process depending on the intendeduse thereof. In order to obtain high-purity hydrogen, CO among thesynthesis gases obtained by the reforming process is separated into CO₂and H₂ by a shift conversion reaction, after which CO₂ is separated andH₂ is separated and purified from impurities (such as CO, H₂O, CH₄,etc.) remaining in the reaction system.

Typical processes for the separation and purification of hydrogeninclude a pressure swing adsorption (PSA) process and a membraneseparation process. In the pressure swing adsorption process, rawmaterial gas is passed through an adsorption column packed with anadsorbent under high pressure, while components with high selectivityare adsorbed onto the adsorbent, and desired components with lowselectivity are discharged from the adsorption column. However, in thisprocess, an equilibrium reaction occurs at a high temperature of about800° C., a large-scale complicated system is used, the number oftreatment processes and apparatuses is increased, a high installationcost is required, and the maintenance and repair of apparatuses aredifficult. In addition, high-purity hydrogen is not obtained, thusmaking it difficult to provide a sufficient amount of high-purityhydrogen. Meanwhile, the membrane separation processes which arecurrently used in practice mostly perform the separation andpurification of hydrogen through a Pd—Ag alloy membrane, ahydrogen-permeable alloy membrane. However, Pd is expensive and is notabundant in nature, and thus the development of a material to substitutefor Pd is requested.

Meanwhile, processes of separating gases from each other using zeoliteshave been attempted. Zeolite is crystalline, and thus has a uniformstructure and a uniform pore size and shape. The pore opening size ofzeolite is primarily determined according to the framework structure,also varies depending on the kind and degree of exchange of cations.Among the selective adsorption properties of zeolite, the most importantis that a material larger than the pore opening cannot enter the pore sothat it is not adsorbed onto zeolite. Different gases have differentmolecular sizes, and different zeolites also have different pore openingsizes. Thus, when zeolite is suitably selected, it can separate a gasmixture into components according to molecular size. Also, due to theenergy interaction between cations and polar or polarizable adsorbents,these adsorbents are adsorbed with a mixture of chemical species havinglow polarity or polarizability. This molecular sieve effect is aninherent property which appears because zeolite is a crystallinematerial and has a pore size similar to the molecular size thereof, andthis molecular sieve effect is effectively used in the separation andpurification field. However, a zeolite that selectively adsorbs hydrogengas has not yet been found.

DISCLOSURE OF INVENTION Technical Problem

It is an object of the present invention to provide a novel porousgallosilicate material whose content of positive trivalent frameworkelements (particularly gallium) is higher than those of known zeoliteshaving the natrolite structure.

Another object of the present invention is to provide a method forpreparing a novel porous gallosilicate.

Still another object of the present invention is to provide the use of anovel porous gallosilicate as either an ion exchanger or an adsorbentfor selectively adsorbing small gaseous molecules such as hydrogen fromgas mixtures.

Still another object of the present invention is to provide a process ofselectively separating high-purity hydrogen and/or high-purity heliumfrom a gas mixture by adsorption using a novel zeolite in a moreeconomical manner.

Technical Solution

To achieve the above objects, the present invention provides a processof selectively separating hydrogen and/or helium from a gas mixturecontaining hydrogen and/or helium, the process comprising bringing thegas mixture into contact with a natrolite-based zeolite.

In the present invention, the natrolite-based zeolite is prepared usinga mixture comprising a source of an alkali metal or alkaline earth metal(M), an oxide of a trivalent element (X), an oxide of a tetravalentelement (Y), and water, in which the mixture has the following molarratio composition:YO₂/X₂O₃=0.5˜100;  (i)H₂O/YO₂=1˜100; and  (ii)M₂O/YO₂=0.1˜10.  (iii)

In an embodiment of the present invention, the alkali metal or alkalineearth metal may be selected from among, for example, Li, Na, K, Ru, Mgand Ca. Also, the trivalent element (X) comprises gallium or aluminum,preferably gallium, and the tetravalent element (Y) comprises silicon.

In an embodiment of the present invention, the natrolite-based zeolitecan be obtained by providing a novel gallosilicate PST-1 (POSTECH number1) zeolite having a framework structure consisting of oxides having amolar ratio shown in the following formula (1), the novel gallosilicatePST-1 zeolite showing X-ray diffraction peak patterns shown in Table 1below:1.0K₂O:1.0Ga₂O₃:2.3˜2.7SiO₂  (1)

TABLE 1 2θ D 100 × I/I₀ 12.9~13.0 6.9~6.8 50~100 14.9~15.0 6.0~5.9 1~3019.8~19.9 4.5~4.4 5~30 20.4~20.5 4.4~4.3 1~5  23.6~23.7 3.8~3.7 1~5 25.9~26.0 3.5~3.4 5~10 27.0~27.1 3.3~3.2 1~5  28.7~28.8 3.2~3.1 1~2029.1~29.2 3.1~3.0 5~10 30.0~30.1 3.00~2.90 55~100 33.2~33.3 2.70~2.651~5  34.2~34.3 2.65~2.60 1~20 35.3~35.4 2.55~2.50 5~20 35.4~35.52.55~2.50 5~20 37.0~37.1 2.45~2.40 1~5  41.5~41.6 2.20~2.15 0~5 42.2~42.3 2.15~2.10 1~5  43.4~43.5 2.10~2.05 0~5  44.4~44.5 2.05~2.001~5  46.6~46.7 1.95~1.90 0~5 wherein θ, d and I indicate Bragg angle, lattice distance, and x-raydiffraction peak intensity, respectively.

In the present invention, the gallosilicate PST-1 zeolite has aframework Si/Ga ratio of 1.2˜1.3, indicating that the content of thepositive trivalent element in the zeolite is significantly higher thanthose in existing zeolites having the natrolite structure. Thegallosilicate PST-1 zeolite is completely dehydrated even when it isheat-treated at very low temperatures (60° C. in a vacuum, and 175° C.in air), thus showing a decrease in volume of about 16%. When it isexposed to air for about 30 minutes, it includes uniform pores having asize of about 3.0 Å, because it has a reversible water (H₂O) adsorptioncapacity of about 7 wt %. Also, the PST-1 zeolite can stably maintainits structure up to a high temperature of at least 800° C. despites itshigh gallium content, and thus it is useful not only as an ionexchanger, but also as an adsorbent for selectively separating smallgaseous molecules such as hydrogen from gas mixtures.

All powder X-ray diffraction data, including the powder X-raydiffraction patterns, which are described in the present invention, weremeasured by a standard X-ray diffraction method using copper Kαradiation as a radiation source with an X-ray tube operating 30 kV and40 mA. The X-ray diffraction peak was measured on a compressed powdersample at a speed of 5° (2θ) per minute, and d and I were calculatedfrom the 2θ value and peak height of the observed X-ray diffractionpeak.

In the present invention, the PST-1 zeolite preferably has X-raydiffraction patterns shown in Table 2 below.

TABLE 2 2θ D 100 × I/I₀ 12.9~13.0 6.9~6.8 100 19.8~19.9 4.5~4.4  5~1020.4~20.5 4.4~4.3 1~5 25.9~26.0 3.5~3.4 10~15 29.1~29.2 3.1~3.0  5~1030.0~30.1 3.00~2.90 55~60 34.2~34.3 2.65~2.60 1~5 35.3~35.4 2.55~2.50 5~10 35.4~35.5 2.55~2.50 10~15 37.0~37.1 2.45~2.40 1~5 44.4~44.52.05~2.00 1~5

In an embodiment of the present invention, the PST-1 zeolite ispreferably obtained by heating a compound represented by the followingformula (2) at a temperature of 100˜200° C. for 0.5˜10 days:xK₂O:yGa₂O₃:10.0SiO₂ :zH₂O  (2)wherein x=5˜12 moles, y=0.5˜5.0 moles, and z=60˜300 moles.

In an embodiment of the present invention, the compound of formula (2)may be prepared by adding potassium hydroxide (KOH) aqueous solution togallium oxide (Ga₂O₃) at a ratio of 5˜12 moles (calculated as oxide(K₂O)) relative to 0.5˜5.0 moles of gallium oxide (Ga₂O₃), dissolvingthe mixture at a temperature of 100±10° C., adding a colloidal silicasol or amorphous silica slowly thereto over 5˜10 minutes at a ratio of10 moles relative to 0.5˜2.0 moles of the gallium oxide, and stirringthe resulting mixture for 4˜48 hours.

The prepared compound of formula (2) is transferred into a Teflonreactor which is then placed in a stainless steel container in which thecompound is then heated at 100˜200° C. for 0.5˜10 days, thus preparingthe gallosilicate PST-1 zeolite of the present invention.

In a preferred embodiment of the present invention, when the compound offormula (2) has the composition shown in the following formula (3), thesynthesis of a pure PST-1 zeolite is easily achieved by heating thecompound at 150° C. for 0.5˜3 days:8.0K₂O:1.0˜2.0Ga₂O₃:10.0SiO₂:100˜200H₂O  (3)

In other embodiments of the present invention, the natrolite-basedzeolite is a TNU-3 (Taejon University Number 3) or TNU-4 (TaejonUniversity Number 4) gallosilicate zeolite described in the presentinventor's paper “Chem. Mater., 2000, Vol. 12, pp. 2292; and J. Am.Chem. Soc., 2004, Vol. 126, pp. 13742”.

In the present invention, the TNU-3 and TNU-4 zeolites arenatrolite-based zeolites having a framework Si/Ga ratio slightly higherthan 1.5 and have excellent ability to selectively exchange monovalentor divalent ions, a reversible steam adsorption capacity of 7.0 wt % ormore at room temperature, and high thermal stability (maintaining itsframework structure even at a high temperature of 500° C. or higher). Inaddition, these zeolites can be used as alkylation and isomerizationcatalysts for hydrocarbons and have excellent denitrification activity.For the methods for synthesizing TNU-3 and TNU-4 zeolites and thecharacteristics of these zeolites, reference is made to the presentinventor's paper.

In the present invention, the natrolite-based silicate zeolite ispreferably used after it has been dehydrated in order to promoteselective adsorption. This dehydration process is generally performed byheating the zeolite at a temperature of 170° C. or higher for apredetermined time in the presence of inert gas. As used herein, theterm “inert gas” means a gas that causes no change in the latticestructure or cations of the zeolite during the high-temperature heatingof the zeolite. Typical examples of inert gas include helium, nitrogenand argon.

The dehydrated PST-1 zeolite can show X-ray diffraction patterns shownin Table 3 below.

TABLE 3 2 θ d 100 × I/I₀ 13.8 6.40 83 15.0 5.91 26 19.6 4.52 7 20.5 4.3232 22.1 4.02 45 28.1 3.17 14 28.8 1.30 100 30.5 2.93 29 32.2 2.78 8235.2 2.55 18 38.0 2.37 14 39.3 2.29 26 39.4 2.29 16 41.7 2.27 9 42.12.14 13 45.8 1.98 12 48.9 1.86 6

In Table 3 above, θ, d and I indicate Bragg angle, lattice distance, andX-ray diffraction peak intensity, respectively. All powder X-raydiffraction data, including the powder X-ray diffraction patterns, whichare described in the present invention, were measured by a standardX-ray diffraction method using copper Kα radiation as a radiation sourcewith an X-ray tube operating 30 kV and 40 mA. The X-ray diffraction peakwas measured on a compressed powder sample at a speed of 5° (2θ) perminute, and d and I were calculated from the 2θ value and peak height ofthe observed X-ray diffraction peak.

The structure of the dehydrated PST-1 zeolite, determined by theabove-described X-ray diffraction data, is shown in FIG. 1. Thedehydrated PST-1 zeolite contains uniform pores having a size smallerthan 2.0 Å, so that it does not adsorb large gaseous molecules such asargon or carbon dioxide, but it has a very flexible structure so that ithas the property of adsorbing only small gaseous molecules, particularlyhydrogen.

The TNU-3 zeolite and the TNU-4 zeolite can be completely dehydrated byheating them at a temperature of 300° C. for a predetermined time in thepresence of inert gas. The results of X-ray diffraction measurement ofthe dehydrated TNU-3 zeolite and TNU-4 zeolite are shown in Tables 4 and5, respectively.

TABLE 4 2 θ d 100 × I/I₀ 13.4 6.61 60 14.9 5.96 100 19.0 4.68 17 20.04.42 66 21.2 4.18 21 27.0 3.30 4 27.7 3.21 35 28.4 3.15 22 30.0 2.98 3230.9 2.89 87 34.4 2.61 20 36.5 2.46 15 39.7 2.27 3 40.7 2.21 12 43.42.08 2 45.6 1.99 3 47.8 1.90 5

TABLE 5 2 θ d 100 × I/I₀ 13.5 6.55 15 15.0 5.91 100 19.4 4.58 8 20.14.42 19 20.3 4.39 19 21.6 4.12 12 27.6 3.23 23 28.2 3.17 8 28.6 2.12 1930.1 2.97 30 30.9 2.89 28 31.3 2.86 28 34.4 2.61 11 34.7 2.59 6 36.32.47 6 37.1 2.42 7 41.2 2.19 14 48.2 1.89 5 49.3 1.85 4

In one aspect, the present invention provides the use of thenatrolite-based zeolite as an adsorbent for selectively adsorbinghydrogen and/or helium.

In another aspect, the present invention provides an adsorbentcomprising the natrolite-based zeolite.

In still another aspect, the present invention provides a process ofseparating a gas mixture into components using the natrolite-basedzeolite. The process of separating the gas mixture according to thepresent invention is characterized in that a gas mixture, such as a gasmixture containing hydrogen and/or helium gas, a gas mixture consistingof hydrogen and carbon dioxide, a gas mixture consisting of hydrogen andargon, or a gas mixture consisting of helium and argon, is brought intocontact with the natrolite-based zeolite, thus separating the gasmixture into components.

In an embodiment of the present invention, the separation of a gasmixture into components comprises a process of extracting a non-adsorbedcomponent, and a process of recovering a component adsorbed onto thezeolite material. In an embodiment of the present invention, therecovered component is hydrogen and/or helium, and is hydrogen in thecase of separation from a hydrogen/helium mixture.

The natrolite-based zeolite of the present invention shows a fasterdiffusion rate for a component, which is preferentially adsorbed, than acomponent which is not preferentially adsorbed. The component that isrecovered may be either the component which is preferentially adsorbedor the component which is not preferentially adsorbed.

In the present invention, the gas adsorption on the zeolite can beperformed in the temperature range from −100 to 800° C., preferably from−50 to 500° C., more preferably from 0 to 300° C., and most preferablyat room temperature.

In the present invention, the process of separating gas by adsorptionmay be used in pressure swing adsorption (PSA), multi-stage pressureswing adsorption, single-stage membrane separation, multi-stage membraneseparation and fluidized-bed systems.

Advantageous Effects

According to the present invention, a gallosilicate zeolite having thenatrolite structure is synthesized which rapidly adsorbs hydrogen atroom temperature so as to separate hydrogen gas from gaseous moleculessuch as argon or carbon dioxide, which are slightly larger than hydrogengas. The use of such properties of the zeolite makes it possible todevelop a more economical process for producing high-purity hydrogen.

According to the present invention, the property of the natrolite-basedzeolite that selectively adsorbs hydrogen or helium was found. Also, aprocess of separating hydrogen and/or helium from a gas mixture byselective adsorption using the natrolite-based zeolite is provided.

The process for separating hydrogen and/or helium according to thepresent invention can be performed at low temperature, indicating thatit can be operated in a cost-effective manner.

According to the present invention, a novel natrolite-based zeolitecapable of adsorbing small molecules such as hydrogen is provided.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows the structure of a dehydrated PST-1 zeolite. In FIG. 1,gray: Si and Ga, red: O, and pink: K.

FIG. 2 shows the amounts of gases as a function of time when a PST-1zeolite treated according to Example 4 of the present invention was usedto separate hydrogen from argon at 30° C.

FIG. 3 shows the amounts of gases as a function of time when a PST-1zeolite treated according to Example 5 of the present invention was usedto separate helium from argon at 30° C.

FIG. 4 shows the amounts of gases as a function of time when a PST-1zeolite treated according to Example 6 of the present invention was usedto separate hydrogen from helium at 30° C.

FIG. 5 shows the amounts of gases as a function of time when a PST-1zeolite treated according to Example 7 of the present invention was usedto separate hydrogen, carbon dioxide and helium from each other at 30°C.

FIG. 6 shows the amounts of gases as a function of time when a PST-1zeolite treated according to Example 8 of the present invention was usedto separate hydrogen from argon at 30° C.

FIG. 7 shows the amounts of gases as a function of time when a PST-1zeolite treated according to Example 9 of the present invention was usedto separate hydrogen from argon at 30° C.

FIG. 8 shows the amounts of gases as a function of time when a TNU-3zeolite treated according to Example 10 of the present invention wasused to separate hydrogen from argon at 30° C.

FIG. 9 shows the amounts of gases as a function of time when a TNU-4zeolite treated according to Example 11 of the present invention wasused to separate hydrogen from argon at 30° C.

BEST MODE Example 1 Preparation of PST-1 zeolite

In a plastic beaker, 22.2 g of 45 wt % potassium hydroxide (KOH) aqueoussolution was added to 6.21 g of water and stirred for 5 minutes, andthen 2.08 g of gallium oxide (Ga₂O₃) was added thereto, and the mixturewas heated at 100° C. for 12 hours. The obtained transparent solutionwas cooled slowly to room temperature, and 16.7 g of colloidal silicasol (Ludox AS-40) was added slowly thereto, and then the mixture wasstirred for 24 hours, thereby obtaining a reaction mixture having thecomposition shown in the following formula (4). Then, the obtainedreaction mixture was transferred into a Teflon reactor which was thenplaced in a stainless steel container in which the reaction mixture wasthen heated at 150° C. for 3 days while it was rotated at 60 revolutionsper minute. Then, the obtained solid product was washed repeatedly withwater and dried at room temperature.8.0K₂O:1.0Ga₂O₃:10.0SiO₂:150H₂O  (4)

The solid powder obtained in Example 1 was subjected to X-raydiffraction measurement, and the results of the measurement are shown inTable 6 below.

TABLE 6 2θ d 100 × I/I₀ 12.9 6.9 100 15.0 5.9 3 19.8 4.4 5 20.4 4.3 323.7 3.8 1 25.9 3.4 13 27.1 3.3 2 28.7 3.10 2 29.1 3.05 9 30.1 2.95 5933.2 2.70 2 34.2 2.60 4 35.3 2.50 8 35.4 2.40 10 37.0 2.30 2 39.0 2.150.4 41.5 2.10 0.5 42.2 2.05 1.26 43.4 2.05 0.75 44.4 2.00 1.89 46.7 1.950.80

In order to examine the composition of the sample obtained in Example 1,the sample was subjected to elemental analysis, and the results of theanalysis are shown in the following formula (5):1.0K₂O:1.0Ga₂O₃:2.56SiO₂:1.26H₂O  (5)

Example 2 Preparation of PST-1 Zeolite

In a plastic beaker, 22.2 g of 45 wt % potassium hydroxide (KOH) aqueoussolution was added to 6.21 g of water and stirred for 5 minutes, andthen 4.17 g of gallium oxide (Ga₂O₃) was added thereto, and the mixturewas heated at 100° C. for 12 hours. The obtained transparent solutionwas cooled slowly to room temperature, and 16.7 g of colloidal silicasol (Ludox AS-40) was added slowly thereto, and then the mixture wasstirred for 24 hours, thereby obtaining a reaction mixture having thecomposition shown in the following formula (6). Then, the obtainedreaction mixture was transferred into a Teflon reactor which was thenplaced in a stainless steel container in which the reaction mixture wasthen heated at 150° C. for 1 day while it was rotated at 60 revolutionsper minute. Then, the obtained solid product was washed repeatedly withwater and dried at room temperature.8.0K₂O:2.0Ga₂O₃:10.0SiO₂:150H₂O  (6)

The solid powder obtained in Example 1 was subjected to X-raydiffraction measurement, and the results of the measurement are shown inTable 7 below.

TABLE 7 2θ d 100 × I/I₀ 12.9 6.9 57 15.0 5.9 29 19.8 4.4 20 20.4 4.3 223.7 3.8 2 25.9 3.4 5 27.0 3.3 5 28.6 3.10 16 29.0 3.05 6 30.1 2.95 10033.2 2.70 1 34.2 2.60 20 35.3 2.50 12 35.4 2.40 16 37.0 2.30 2 39.0 2.152 41.7 2.10 0.5 42.2 2.05 1 43.3 2.05 3 43.8 2.05 3 44.4 2.00 2 45.82.00 2

In order to examine the composition of the sample obtained in Example 2,the sample was subjected to elemental analysis, and the results of theanalysis are shown in the following formula (7):1.0K₂O:1.0Ga₂O₃:2.43SiO₂:1.20H₂O  (7).

Example 3 Preparation of PST-1 Zeolite

In a plastic beaker, 36.27 g of 45 wt % potassium hydroxide (KOH)aqueous solution was added to 10.16 g of water and stirred for 5minutes, and then 6.82 g of gallium oxide (Ga₂O₃) was added thereto, andthe mixture was heated at 100° C. for 12 hours. The obtained transparentsolution was cooled to room temperature, and 27.3 g of colloidal silicasol (Ludox AS-40) was added slowly thereto, and then the mixture wasstirred for 24 hours, thereby obtaining a reaction mixture having thecomposition shown in the following formula (8). Then, the obtainedreaction mixture was transferred into a Teflon reactor which was thenplaced in a stainless steel container in which the reaction mixture wasthen heated at 150° C. for 1 day. Then, the obtained solid product waswashed repeatedly with water and dried at room temperature.8.0K₂O:2.0Ga₂O₃:10.0SiO₂:150H₂O  (8)

Example 4 Preparation of TNU-3 Zeolite

In a plastic beaker, 38.40 g of 50 wt % sodium hydroxide (NaOH) aqueoussolution was added to 48.48 g of water and stirred for 5 minutes, andthen 7.50 g of gallium oxide (Ga₂O₃) was added thereto, and the mixturewas heated at 100° C. for 12 hours. The obtained transparent solutionwas cooled to room temperature, and 60.00 g of colloidal silica sol(Ludox AS-40) was added slowly thereto, and then the mixture was stirredfor 24 hours, thereby obtaining a reaction mixture having thecomposition shown in the following formula (9). Then, the obtainedreaction mixture was transferred into a Teflon reactor which was thenplaced in a stainless steel container in which the reaction mixture wasthen heated at 100° C. for 3 days. Then, the obtained solid product waswashed repeatedly with water and dried at room temperature.6.0Na₂O:1.0Ga₂O₃:10.0SiO₂:150H₂O  (9)

Example 5 Preparation of TNU-4 Zeolite

In a plastic beaker, 38.40 g of 50 wt % sodium hydroxide (NaOH) aqueoussolution was added to 48.48 g of water and stirred for 5 minutes, andthen 7.50 g of gallium oxide (Ga₂O₃) was added thereto, and the mixturewas heated at 100° C. for 12 hours. The obtained transparent solutionwas cooled to room temperature, and 60.00 g of colloidal silica sol(Ludox AS-40) was added slowly thereto, and then the mixture was stirredfor 24 hours, thereby obtaining a reaction mixture having thecomposition shown in the formula (9). Then, the obtained reactionmixture was transferred into a Teflon reactor which was then placed in astainless steel container in which the reaction mixture was then heatedat 200° C. for 14 days. Then, the obtained solid product was washedrepeatedly with water and dried at room temperature.

Example 6

160.8 mg of the PST-1 zeolite prepared in Example 3 was charged into afixed-bed microreactor having an inner diameter of 0.64 cm. The contentof the reactor was heated at 450° C. at an argon flow rate of 50 cc/minfor 1 hour, so that the sample was completely dehydrated. The dehydratedmaterial was cooled to room temperature under an argon stream. Theamount of the dehydrated PST-1, measured at room temperature, was 150.0mg. Then, a mixed gas of hydrogen and argon was allowed to flow into thereactor at a flow rate of 100 cc/min and a gaseous hourly space velocity(GHSV) of 26500/hour. The mixed gas was a 4:96 (v/v) mixture of hydrogenand argon. The amount of gas passed through the reactor was analyzedusing a Hiden Analytical HPR20 mass spectrometer. The selective hydrogenadsorption by the PST-1 zeolite is shown in FIG. 2. As can be seentherein, the PST-1 zeolite selectively adsorbed only hydrogen gaswithout adsorbing argon gas.

Example 7

160.8 mg of the PST-1 zeolite prepared in Example 3 was charged into afixed-bed microreactor having an inner diameter of 0.64 cm. The contentof the reactor was heated at 450° C. at an argon flow rate of 50 cc/minfor 1 hour, so that the sample was completely dehydrated. The dehydratedmaterial was cooled to room temperature under an argon stream. Then, amixed gas of helium and argon was allowed to flow into the reactor at aflow rate of 100 cc/min and a gaseous hourly space velocity (GHSV) of26500/hour. The mixed gas was a 4:96 (v/v) mixture of helium and argon.The amount of gas passed through the reactor was analyzed using a HidenAnalytical HPR20 mass spectrometer. The adsorption of helium gas by thePST-1 zeolite is shown in FIG. 3. As can be seen therein, the PST-1zeolite selectively adsorbed only helium gas having a size smaller thanhydrogen gas without adsorbing argon gas.

Example 8

160.8 mg of the PST-1 zeolite prepared in Example 3 was charged into afixed-bed microreactor having an inner diameter of 0.64 cm. The contentof the reactor was heated at 450° C. at an argon flow rate of 50 cc/minfor 1 hour, so that the sample was completely dehydrated. The dehydratedmaterial was cooled to room temperature under an argon stream. Then, amixed gas of hydrogen and helium was allowed to flow into the reactor ata flow rate of 100 cc/min and a gaseous hourly space velocity (GHSV) of26500/hour. The mixed gas was a 4:96 (v/v) mixture of hydrogen andhelium. The amount of gas passed through the reactor was analyzed usinga Hiden Analytical HPR20 mass spectrometer. The adsorption of hydrogengas by the PST-1 zeolite is shown in FIG. 4. As can be seen therein, thePST-1 zeolite more selectively adsorbed hydrogen gas than helium gashaving a smaller size.

Example 9

160.8 mg of the PST-1 zeolite prepared in Example 3 was charged into afixed-bed microreactor having an inner diameter of 0.64 cm. The contentof the reactor was heated at 450° C. at an argon flow rate of 50 cc/minfor 1 hour, so that the sample was completely dehydrated. The dehydratedmaterial was cooled to room temperature under an argon stream. Then, amixed gas of hydrogen, carbon dioxide and helium was allowed to flowinto the reactor at a flow rate of 100 cc/min and a gaseous hourly spacevelocity (GHSV) of 26500/hour. The mixed gas was a 4:4:96 (v/v/v)mixture of hydrogen, carbon dioxide and helium. The amount of gas passedthrough the reactor was analyzed using a Hiden Analytical HPR20 massspectrometer. The selective adsorption of hydrogen gas by the PST-1zeolite is shown in FIG. 5. As can be seen therein, the PST-1 zeolitemore selectively adsorbed hydrogen gas than helium gas without adsorbingcarbon dioxide gas.

Example 10

160.8 mg of the PST-1 zeolite prepared in Example 3 was charged into afixed-bed microreactor having an inner diameter of 0.64 cm. The contentof the reactor was heated at 450° C. at an argon flow rate of 50 cc/minfor 1 hour, so that the sample was completely dehydrated. The dehydratedmaterial was cooled to room temperature under an argon stream. Then, amixed gas of hydrogen and argon was allowed to flow into the reactor ata flow rate of 50 cc/min and a gaseous hourly space velocity (GHSV) of13250/hour. The mixed gas was a 4:96 (v/v) mixture of hydrogen andargon. The amount of gas passed through the reactor was analyzed using aHiden Analytical HPR20 mass spectrometer. The selective adsorption ofhydrogen gas by the PST-1 zeolite, measured when the flow rate of themixed gas was reduced to 50 cc/min, is shown in FIG. 6. As can be seentherein, the time of adsorption of hydrogen gas increased.

Example 11

160.8 mg of the PST-1 zeolite prepared in Example 3 was charged into afixed-bed microreactor having an inner diameter of 0.64 cm. The contentof the reactor was heated at 450° C. at an argon flow rate of 50 cc/minfor 1 hour, so that the sample was completely dehydrated. The dehydratedmaterial was cooled to room temperature under an argon stream. Then, amixed gas of hydrogen and argon was allowed to flow into the reactor ata flow rate of 150 cc/min and a gaseous hourly space velocity (GHSV) of13250/hour. The mixed gas was a 4:96 (v/v) mixture of hydrogen andargon. The amount of gas passed through the reactor was analyzed using aHiden Analytical HPR20 mass spectrometer. The selective adsorption ofhydrogen gas by the PST-1 zeolite, measured when the flow rate of themixed gas was increased to 150 cc/min, is shown in FIG. 7. As can beseen therein, the PST-1 zeolite very quickly adsorbed hydrogen gas.

Example 12

500.0 mg of the TNU-3 zeolite prepared in Example 4 was charged into afixed-bed microreactor having an inner diameter of 0.64 cm. The contentof the reactor was heated at 300° C. at an argon flow rate of 100 cc/minfor 1 hour, so that the sample was completely dehydrated. The dehydratedmaterial was cooled to room temperature under an argon stream. Then, amixed gas of hydrogen and argon was allowed to flow into the reactor ata flow rate of 100 cc/min and a gaseous hourly space velocity (GHSV) of19500/hour. The mixed gas was a 4:96 (v/v) mixture of hydrogen andargon. The amount of gas passed through the reactor was analyzed using aHiden Analytical HPR20 mass spectrometer. The selective adsorption ofhydrogen gas by the TNU-3 zeolite is shown in FIG. 8. As can be seentherein, the TNU-3 zeolite selectively adsorbed hydrogen gas.

Example 13

500.0 mg of the TNU-4 zeolite prepared in Example 5 was charged into afixed-bed microreactor having an inner diameter of 0.64 cm. The contentof the reactor was heated at 300° C. at an argon flow rate of 100 cc/minfor 1 hour, so that the sample was completely dehydrated. The dehydratedmaterial was cooled to room temperature under an argon stream. Then, amixed gas of hydrogen and argon was allowed to flow into the reactor ata flow rate of 100 cc/min and a gaseous hourly space velocity (GHSV) of19500/hour. The mixed gas was a 4:96 (v/v) mixture of hydrogen andargon. The amount of gas passed through the reactor was analyzed using aHiden Analytical HPR20 mass spectrometer. The selective adsorption ofhydrogen gas by the TNU-4 zeolite is shown in FIG. 9. As can be seentherein, the TNU-4 zeolite selectively adsorbed hydrogen gas.

Example 14 Analysis of Characteristics of PST-1 Zeolite

When the solid powder obtained in Example 1 was subjected to thermalanalysis, about 7 wt % of water was desorbed from the powder at atemperature of 200° C. or lower. Also, when the same sample wassubjected to heating X-ray diffraction measurement, the unit latticeconstant of the PST-1 zeolite at room temperature was calculated to bea=13.729 Å, c=6.572 Å. However, when the sample was heated to 60° C. ina vacuum of 10⁻³ Torr, the water of the PST-1 zeolite was mostlyremoved. The unit lattice constant calculated from the X-ray diffractionpattern measured at 100° C. was compared with the unit lattice constantat room temperature, and as a result, a decrease in unit lattice volumeof 16.3% was found. In addition, it was observed that the PST-1 zeolitestably maintained its structure up to a temperature of at least 800° C.Also, when the PST-1 zeolite was cooled to room temperature and thenexposed to air, it was restored to the original state within 30 minutesby adsorbing water.

The invention claimed is:
 1. A process of selectively separatinghydrogen or helium from a gas mixture containing hydrogen or helium, theprocess comprising bringing the gas mixture into contact with anatrolite-based zeolite.
 2. The process of claim 1, wherein the hydrogenor helium is separated by adsorption on the natrolite-based zeolite. 3.The process of claim 1, wherein the natrolite-based zeolite is preparedusing a mixture comprising a source of an alkali metal or alkaline earthmetal (M), an oxide of a trivalent element (X), an oxide of atetravalent element (Y), and water, in which the mixture has thefollowing molar ratio composition:YO₂/X₂O₃=0.5˜100;  (i)H₂O/YO₂=1˜100; and  (ii)M₂O/YO₂=0.1˜10.  (iii)
 4. The process of claim 3, wherein X comprisesgallium or aluminum, and Y comprises silicon.
 5. The process of claim 1,wherein the natrolite-based zeolite is a natrolite-based gallosilicate.6. The process of claim 1, wherein the separation occurs at atemperature ranging from −100 to 800° C.
 7. The process of claim 6,wherein the adsorption occurs at room temperature.
 8. A process ofseparating hydrogen or helium from a gas mixture containing hydrogen orhelium, the process comprising bringing the gas mixture into contactwith a gallosilicate PST-1 zeolite consisting of oxides having a molarratio shown in the following formula (1), the gallosilicate PST-1zeolite being characterized by X-ray diffraction patterns includinglattice distances shown in Table 11 below:1.0K₂O:1.0Ga₂O₃:2.3˜2.7SiO₂  (1) TABLE 11 2θ D 100 × I/I₀ 12.9~13.06.9~6.8 100 19.8~19.9 4.5~4.4  5~10 20.4~20.5 4.4~4.3 1~5 25.9~26.03.5~3.4 10~15 29.1~29.2 3.1~3.0  5~10 30.0~30.1 3.00~2.90 55~6034.2~34.3 2.65~2.60 1~5 35.3~35.4 2.55~2.50  5~10 35.4~35.5 2.55~2.5010~15 37.0~37.1 2.45~2.40 1~5 44.4~44.5 2.05~2.00 1~5

wherein θ, d and I indicate Bragg angle, lattice distance, and x-raydiffraction peak intensity, respectively.
 9. The process of claim 8,wherein the PST-1 zeolite has a lattice structure shown in Table 12below: TABLE 12 2θ D 100 × I/I₀ 12.9~13.0 6.9~6.8 50~100 14.9~15.06.0~5.9 1~30 19.8~19.9 4.5~4.4 5~30 20.4~20.5 4.4~4.3 1~5  23.6~23.73.8~3.7 1~5  25.9~26.0 3.5~3.4 5~10 27.0~27.1 3.3~3.2 1~5  28.7~28.83.2~3.1 1~20 29.1~29.2 3.1~3.0 5~10 30.0~30.1 3.00~2.90 55~100 33.2~33.32.70~2.65 1~5  34.2~34.3 2.65~2.60 1~20 35.3~35.4 2.55~2.50 5~2035.4~35.5 2.55~2.50 5~20 37.0~37.1 2.45~2.40 1~5  41.5~41.6 2.20~2.150~5  42.2~42.3 2.15~2.10 1~5  43.4~43.5 2.10~2.05 0~5  44.4~44.52.05~2.00 1~5  46.6~46.7 1.95~1.90  0~5. 


10. The process of claim 8, wherein the PST-1 zeolite is used afterdehydration.
 11. A process of separating hydrogen from a gas mixturecontaining hydrogen, the process comprising bringing the gas mixtureinto contact with a TNU-3 zeolite and/or a TNU-4 zeolite.
 12. Theprocess of claim 11, wherein the TNU-3 and TNU-4 are used afterdehydration.